Polypropylene having a high degree of unsaturation



RATE OF FLOW grams per /0 min.

Nov. 19, 1968 H. J. HAGEMEYER, JR.. ETAL 3,412,078

POLYPROPYLENE HAVING A HIGH DEGREE OF UNSATURATION Filed Feb. 16, 1966POL YPROPYLENES OF THIS INVENTION PRIOR ART POLYPROPYLENE 5 SHEERSTRESS, dynes/cm x m HUGH J. HAGEMEYE'R JR.

I NVENTORS United States Patent 3,412,078 POLYPROPYLENE HAVING A HIGHDEGREE OF UNSATURATION Hugh J. Hagemeyer, Jr., and Marvin B. Edwards,Longview, Tex., assignors to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey Continuation-in-part of application Ser. No.210,835,

July 18, 1962. This application Feb. 16, 1966, Ser.

8 Claims. (Cl. 26093.7)

ABSTRACT OF THE DISCLOSURE Polypropylene having a high degree ofunsaturation which has outstanding film-forming and flow properties.

This application is a continuation-in-part of application S.N. 210,835,filed July 18, 1962, now abandoned, which is a continuation-in-part ofapplication S.N. 756,522, filed Aug. 22, 1958, now abandoned, which is acontinuationin-part of application S.N. 555,228, filed Dec. 27, 1955,now abandoned. This application is also a continuationpart ofapplication S.N. 230,702, filed Oct 15, 1962, now abandoned, which is acontinuation-in-part of application S.N. 152,001, filed Nov. 13, 1961,now abandoned.

This invention relates to a new polymer prepared from propylene. In aspecific aspect this invention relates to a new polypropylene that hasoutstanding film-forming and flow properties.

Heretofore propylene has been polymerized in the presence of a Widevariety of catalysts in an effort to prepare a polymer that is as nearlystereoregular as possible. Stereospecific catalysts have been preparedand used for this purpose and the object has been to produce a propylenepolymer that is highly crystalline, insoluble in boiling n-heptane, andhaving a stereoregular structure. Metal oxide catalysts and coordinationtype catalysts containing a transition metal halide have been used forthis purpose. Illustrations of the types of propylene polymers that havebeen prepared in this manner can be found in British Patent 810,023 andUS. Patents 3,112,300 and 3,112,301. These patents describe thepreparation of a socalled isotactic polypropylene in which all of theasymmetric carbon atoms have the same steric configuration. Attemptshave been made to increase the stereoregularity of polypropylene on thetheory that a more regular structure would improve the properties of thepolymer. These efforts have achieved some success in that it has beenpossible to realize improvements in the stiffness and tensile strengthof the polymer as a result of greater stereoregularity. On the otherhand, for some applications of these prior art types of polypropyleneits use has been rather seriously restricted. For example, highlystereoregular polypropylene has only a rather limited use as a filmbecause of the poor quality of the film such as its poor gloss, haze,transparency and impact strength and the high embrittlement of the filmafter ageing. Highly stereoregular polypropylene also has relativelypoor flow properties, and as a consequence, it has not been possible forthis type of polypropylene to achieve its fullest commercialutilization.

It is an object of this invention to provide a new and improvedpropylene polymer having a structure different from previously knownpropylene polymers. It is another object of this invention to provide anew and improved propylene polymer having outstanding film-forming andflow properties. It is a further object of this invention to provide anew and improved propylene polymer that is characterized by a higherdegree of unsaturation in the polymer chain than the prior art types ofpropylene poly- 3,412,078 Patented Nov. 19, 1968 mer. It is still afurther object of this invention to provide a propylene polymer havingoutstanding film-forming and flow properties as well as the advantageousproperties of highly stereoregular propylene polymers such as highstiffness, high tensile strength, and high softening point. Otherobjects of this invention will be apparent from the detailed descriptionthat follows.

In accordance with this invention we have found that a new propylenepolymer can 'be produced having substantial crystallinity and beinginsoluble in boiling hexane and having a total weight percent vinyl andvinylidene unsaturation between 0.04 and 0.27 with 0.025 to 0.065 weightpercent of said unsaturation being vinyl unsaturation. As a consequenceof the high percentage of unsaturation in the polymer chain of ourpolypropylene, we have found that we can overcome some of thedeficiencies of prior art types of polypropylene by greatly improvedfilm and flow properties. Our new polypropylene is highly crystallineand it is insoluble in boiling hexane. Our polypropylene possesses thedesirable properties of the highly stereoregular types of polypropyleneprepared prior to our invention, and at the same time our polypropylenehas greatly improved film and flow properties when compared with theprior art types of polypropylene.

The polypropylene of our invention is produced by a solution process attemperatures sufiiciently high that during the reaction thepolypropylene is dissolved in the reaction solvent or diluent. Ourspecific examples illustrate that the polymerization reaction is carriedout at carefuly selected conditions of temperature and pressure and inthe presence of a lithium-type of catalyst in combination with a reducedtransition metal halide. The preferred catalyst contains either lithiumaluminum hydride or lithium aluminum heptahydride with a reducedtitanium halide such as titanium trichloride. For best results an alkalimetal halide such as sodium fluoride is employed in the catalyst. Thepolymerization reaction is carried out by contacting the propylene witha suitable lithium-type catalyst in a liquid hydrocarbon solvent at atemperature of at least 'C. and usually not above 250 C. After thedesired molecular weight of the polymer has been achieved as measured bythe inherent viscosity, the polypropylene is separated from catalyst byfiltration or other suitable means and the hydrocarbon solvent is thenstripped from the polymer. The lithiumztitanium ratio in the catalyst isvaried within the range of 2:1 to 1:2 and the amount of sodium fluorideis sufiicient to increase substantially the stereospecificity of thecatalyst. Aliphatic or aromatic hydrocarbon solvents may be used in thepolymerization reaction. A preferred solvent is a mineral spiritsfraction having a boiling point of 180 to 200 C. The polymerizationreaction is carried out either batchwise or continuously at at pressurevarying from atmospheric to 200 atmos. The preferred polymerizationpressure is about 1000 p.s.i.

The propylene polymer that is produced in the manner described above isinitially a mixture of amorphous and highly crystalline polypropylenewhich can be separated by extraction. The total or gross polymer can beused to form useful articles by injection molding, extruding, and thelike. The gross polymer contains greater than 70% by Weight ofcrystalline polymer and has many uses. It is desirable to extract atleast a portion of the amorphous polymer from the gross polymer. Theextraction can be accomplished with hexane at or near its boiling point,and any amount of the amorphous polymer can be separated from thecrystalline polymer in this manner. The crystalline polymer is insolublein boiling hexane, and it has a total weight precent vinyl andvinylidene unsaturation between 0.04 and 0.27 with 0.025 to 0.065 weightpercent of said unsaturation being vinyl unsaturation.

The propylene polymers within the scope of this invention arecharacterized by a high degree of unsaturation which is made up of bothvinyl and vinylidene unsaturation as measured by infrared techniques.Table I demonstrates the total percent unsaturation of propylenepolymers of this invention, and this total unsaturation is compared withthe total unsaturation in known types of polypropylene that havebeenavailable commercially.

TABLE I Percent Percent Percent Inherent Vinyl Vinylidene TotalViscosity Unsaturation Unsaturation Unsaturation IOLYPROPYLENES OF THISINVENTION It is apparent that the high percentage total unsaturation andespecially the high vinyl saturation is found only in the tpropylenepolymers of this invention, and not in the propylene polymers that wereavailable prior to this invention. Although the total unsaturation ofthe prior art propylene polymers can be increased by thermal degradationof the polymer, the increase in unsaturation that results from thermaldegradation is in the vinylidene unsaturation with the vinylunsaturation remaining essentially unchanged. For example, a sample ofprior art polypropylene having a relatively low total unsaturation andhaving an I.V of 1.8 was thermally degraded at a temperature of 230 C.for 46 hrs. to form a product having an I.V. of 1.2. The unsaturation ofthe polymer was measured before and after thermal degradation, and thefollowing results were observed.

Percent Percent Vinyl vinylidene Percent Total Unsaturation UnsaturationUnsaturation Before degradation 0.005 O. 003 0.008 Alter degradation 0.005 0. 048 0. 053

It should be observed that the total unsaturation of the gross or totalpolymer mixture of this invention is higher than the total unsaturationof the crystalline hexane insoluble polypropylene within the scope ofthis invention. This diiference in unsaturation is shown by thefollowing table which includes the unsaturation of the gross polymermixture and the hexane insoluble fraction of that mixture.

Percent Percent Vinyl Vinylidene Percent Total Unsaturation UnsaturationUnsaturation Total polymer mixture. 0. 051 0. 055 0. 106Hexane-insoluble polypropylene 0. 041 0. 035 0. 076

Polypropylene of This Prior Art Invention Polypropylene roomtemperature:

(1) 24 hours 38 35 (2) 6 weeks 35 1t) (3) 3 months 36 13 (4) 6 months 305 The improved optical properties and lack of embrittlement of film madefrom polypropylene of our invention are a result of the outstanding flowproperties of our polymer and the differences in crystallinity attainedunder normal conditions.

The flow properties of polypropylenes of this invention are superior tothose of prior art polypropylcnes as shown by the following data.Polypropylenes of this invention and prior art polypropylenes of thesame molecular weights were subjected to various sheer stresses in anextrusion plastometer and the rate of flow measured as shown in FIGURE1.

At low sheer stresses the rates of flow are approximately equivalent;however, as the sheer stresses .are increased and approach thoseencountered in commercial molding equipment, the rate of flow of thepolypropylene of this invention is about 60 percent greater than therate of flow of prior art polypropylenes.

Under normal conditions the polypropylenes of this invention crystallizeat a slower rate and have a lower order of crystallinity than prior artpolypropylenes be cause of the differences in structure. This can beseen by comparing the melting points and crystallization temperatures ofthe polypropylenes of this invention with prior art polypropylenes. Thefollowing data was obtained on a differential scanning calorimeter(DSC). The samples were heated and cooled at a rate of 10 C./minute.

The lower crystallization temperature and lower melting point of ourpolypropylene indicate a slower crystallization process and a lowerorder of crystallinity, respectively, under normal conditions. Thecrystallinity of our polypropylene can be increased by forcing thecrystallization under controlled conditions, such as annealing at ornear the melting point for long periods of time. However, under normalconditions our polypropylene will not .attain the same degree ofcrystallinity as prior are polypropylenes. Therefore, film produced fromour polypropylene retains its impact strength upon ageing, whereas filmproduced from prior art polypropylenes embrittles with age because ofits higher order of crystallinity.

Examples 1 and 2 illustrate the preparation of propylene polymers withinthe scope of our invention.

Example 1 A catalyst mixture was prepared by suspending 0.59 gram(0.0155 mole) of lithium aluminum hydride and 2.41 grams (0.0155 mole)of titanium trichloride in ml. of sweet mineral spirits. The mixture wasactivated by heating to 100 C. in an inert atmosphere and stirring for 1hour with a high-speed stirrer. The activated catalyst mixture wascharged to a 600-ml. rocking autoclave under a blanket of nitrogen. Theautoclave was sealed and 300 ml. of liquid propylene was added at roomtemperature. The autoclave was heated to C. and agitated at thistemperature for 4 hours. The autoclave was then cooled, and the crudereaction product was stirred with 1000 ml. of methanol and filtered. Thecrude polypropylene was Example 2 An 82-gallon autoclave was chargedwith 40 gallons of odorless naphtha and 50 grams of lithium aluminumhydride-titanium trichloride catalyst complex. The catalyst complex wasprepared by mixing lithium aluminum hydride and titanium trichloride ina 1 to 1 mole ratio in odorless naphtha at 30 C. for 2 hours. Aftertrituration of the mixture was complete, the catalyst mixture waselutriated until the purple color of unreacted titanium trichloride wasno longer visible in the overflow solvent. Fifty grams of the remainingcatalyst mixture was charged to the autoclave. Propylene was pressuredin at 400 pounds and 150 C. for a reaction time of 8 hours. The polymersolution in the autoclave was then filtered through a plate and framefilter at 200 C. and 400 p.s.i. The clear colorless polypropylene dopewas let down from 400 pounds pressure at the filter discharge to astirred concentrating vessel. The concentrating vessel was maintained at200 C. while sweeping gaseous propylene heated to 200 C. through thepolymer dope. In this manner all of the solvent was removed from thepolypropylene and the molten polypropylene was extruded through a cutterface and chopped in water to give pellets of polypropylene. The yield ofpolymer was 69 pounds with a specific gravity of 0.910, andcrystallinity of 92 percent. The reaction rate in the above run is equalto 78 grams of polymer per gram of catalyst per hour and the yield ofpolymer is approximately 625 pounds per pound of catalyst or 3100 poundsper pound of lithium aluminum hydride. Unsaturation content of thepolypropylene was 0.045 percent vinyl and 0.030 percent vinylidene.

In Example 3 polypropylene is prepared according to the prior art andthe properties of this polymer should be compared with our product ofExample 4.

Example 3 A solution of 1.8 grams of titanium tetrachloride in 50 ml. ofsweet mineral spirits is added dropwise at a temperature of 510 C. to asolution of 11.4 grams of triethyl aluminum in 150 ml. of sweet mineralspirits. The solution is further diluted to 500 ml. with sweet mineralspirits and charged to a 2-liter stirred autoclave under a blanket ofnitrogen. The autoclave was sealed and 190 grams of liquid propylene wasadded at room temperature. The autoclave was heated to 55-60" C. andagitated at this temperature. After the pressure has fallen from theinitial value'of about atmospheres to about 2 atmospheres, an additional160 grams of propylene are added, and the polymerization is continuedfor hours.

The residual gases are then vented, and 95 grams of methanol are pumpedinto the autoclave. The crude polymerization product is then extractedfrom the autoclave and filtered. The crude polypropylene was washed freeof catalyst residues by repeated extraction with hot methanol and thendried. The polypropylene thus obtained weighed 175 grams and had an ashcontent of 0.18 percent. This polypropylene was then extracted withboiling n-heptane in a Soxhlet-type extractor. The n-heptane-insolubleportion amounting to 35 percent of the total polymer had an inherentviscosity of 2.9 and unsaturation as follows:

Unsaturation, percent Vinyl 0.004

Vinylidene 0.003

Total 0.007

Example 4 A catalyst mixture was prepared by suspending 0.60 gram oflithium aluminum hydride, 2.40 grams of titanium trichloride, and 0.66gram of sodium fluoride in ml. of sweet mineral spirits. The mixture wasdiluted with 900 ml. of sweet mineral spirits and charged to a 2-literstirred autoclave under a blanket of nitrogen. The autoclave was heatedto C. and propylene was pumped in to maintain a pressure of 1000 psi.The polymerization was conducted at these conditions for 4 hours. Theautoclave was then cooled and the crude reaction product was stirredwith 1000 ml. of methanol and filtered. The crude polypropylene waswashed free of catalyst residues by repeated extraction with hotmethanol and then dried. The polypropylene thus obtained weighed 291grams and had an ash content of 0.15 percent, This polypropylene wasthen extracted with boiling hexane in a Soxhlet-type extractor. Thehexane-insoluble portion amounting to 75 percent of the total polymerhad an inherent viscosity of 1.7 and unsaturation as follows:

Unsaturation, percent Vinyl 0.043 Vinylidene 0.032

Total 0.072

The hexane-insoluble portion was then extracted with boiling n-heptane.The heptane-insoluble portion amount- Unsaturation, percent Vinyl 0.035Vinylidene 0.030

Total 0.065

Physical properties were determined on polypropylenes prepared by themethods described in Examples 3 and 4. Results are as follows:

The above properties indicate the lower degree of crystallizationattained by the polypropylenes of this invention under normal conditionsas indicated by the lower density, tensile strength, stitfness, andsoftening point of our polypropylene when compared with prior artpolypropylenes.

The inherent viscosity of the polypropylenes of our invention can bevaried over rather wide limits. For instance, the total polymer can bevaried in inherent viscosity over the range 0.3 to 4.0 with thehexane-soluble portion having an inherent viscosity of 0.1 to 0.6 andthe hexane-insoluble portion having an inherent viscosity of 0.5 to 5.0.

Throughout the specification and claims the polymer unsaturation that isreferred to is measured by infrared spectroscopy. One of the most widelyused methods of detecting carbon-carbon double bonds and ofdifferentiating the various types of unsaturation is through a study ofthe out-of-plane deformation of the attached hydrogen atoms. Infraredabsorptions at 11.0 microns due to --CHCH and at 11.25 microns due to-CRCH are used in this determination. An absorption band of 11.15microns due to crystalline polypropylene interferes in the accuratemeasurement of the absorption bands due to vinyl and vinylideneunsaturation. A differential technique is used cancelling out theinterfering absorption band, and a variable thickness reference samplewas used.

A sample of polypropylene was hydrogenated under such conditions as toproduce a polymer which, for analytical purposes, was completelysaturated, The powdered polymer was placed in a specially preparedwedgeshaped die and heated to 180 C. at 3000 p.s.i. After 10 minutes atthis temperature and pressure the die containing the polymer was cooledby a water quench. The molded specimen is a strip 5 inches long by 1%inches wide. It is wedge shaped along the thickness dimension varyingfrom 0.01 cm. at one end to 0.05 cm. at the other, and it is referred toas the standard wedge.

A 0.3 gram sample of polypropylene is compression molded at 180 C. and3000 p.s.i. pressure. After minutes at this temperature and pressure,the die is cooled in water and the sample is removed. Its thickness ismeasured to :00002 cm.

The molded sample is placed in the sample beam of the infraredinstrument and the standard wedge in the reference beam. The instrumentis set at 8.9 microns and to record at 3 minutes per micron to 9.75microns. If absorption peaks are apparent in the spectrum at 9.07 and9.58 microns, the thickness of the portion of the standard wedge in thereference light path is increased by moving the wedge horizontally. Ifnegative (downscale) peaks are observed, the thickness is decreased.When 100 percent compensation is achieved a straight line from 8.9 to9.75 microns is recorded and the crystallinity of the sample and thestandard wedge as seen by the instrument is identical.

To determine the vinyl and vinylidene unsaturation absorption theinfrared instrument is set to 10.75 microns, and to record at 3 minutesper micron to 11.5 microns. A base line is drawn from 10.75 microns to11.50 microns, and the net (base line) absorption at 11.00 and 11.25microns is determined.

The unsaturation is calculated by the following equations:

Sample thickness (cm.) X00193 Percent, vinylidene C=C Net absorption at11.25 microns Sample thickness (em.)

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof, it willbe understood that variations and modifications can be effected withinthe spiit and scope of the invention as described hereinabove, and asdefined in the appended claims.

We claim:

1. As a composition of matter, a crystalline propylene homopolymerinsoluble in boiling hexane, said propylene homopolymer having bothvinyl and vinylidene unsaturation, the total vinyl and vinylideneunsaturation being between 0.04 and 0.27 weight percent and said vinylunsaturation being 0.025 to 0.065 weight percent.

2. As a composition of matter, a crystalline propylene homopolymerinsoluble in boiling hexane and having both vinyl and vinylideneunsaturation, said homopolymer having a crystallinity as determined byextraction with boiling n-heptane of at least percent by weight, thetotal vinyl and vinylidene unsaturation being between 0.04 and 0.27weight percent, said vinyl unsaturation between 0.025 to 0.085 weightpercent.

3. Molded article prepared from the composition of claim 1.

4. Molded article prepared from the composition of claim 2.

5. Film prepared from the composition of claim 1.

6. Film prepared from the composition of claim 2.

7. Fibers and filaments prepared from the composition of claim 1.

8. Fibers and filaments prepared from the composition of claim 2.

References Cited UNITED STATES PATENTS 3,189,584 6/1965 Shearer 26094.92,825,721 3/1958 Hogan et a1. 26094.9 3,050,471 8/1962 Anderson et a1.260-937 2,909,511 10/1959 Thomas 26093.7 2,886,561 5/1959 Reynolds etal. 26094.9

FOREIGN PATENTS 555,890 9/1957 Belgium. 1,248,850 11/1960 France.

JOSEPH L. SCHOFER, Primary Examiner.

M. B. KURTZMAN, Assistant Examiner.

